1. Field of the Invention
The exemplary embodiment(s) of the present invention relates to a gain controlling system, a sound playback system, and a gain controlling method thereof. More specifically, the exemplary embodiment(s) of the present invention relates to a gain controlling system, a sound playback system, and a gain controlling method thereof which could improve the gain variance curve.
2. Description of the Related Art
With the improvement of the technology, various sound playing systems are widely used, such as stereo systems or computer systems that provide signals to generate sound through the speakers. In the prior arts, the sound volume of the sound signal could be adjusted by using the analog gain controller made by the passive potentiometer. The analog gain controller uses a sliding sheet to touch a thin-film resistor, and the gain magnitude is obtained according to the physical position of the sliding sheet. The potentiometer usually obtains the gain magnitude according the rotation (or sliding) made by the user, and thus the user could not hear the crackling noise.
However, in the prior arts, the computer system usually uses a digital gain control circuit to control the sound volume, as shown in FIG. 1A, which is a structure schematic diagram of the gain controlling system of the prior art.
The gain controlling system 90 comprises a signal input end 91, a signal output end 92, an operational amplifier 93 and change-over switches S1, S2 and S3. The user could obtain different sound signals with different gain by switching different change-over switches S1, S2 or S3, for example, by changing to the change-over switches S2 from the change-over switches S1. But, as shown in FIG. 1B which is a gain curve diagram showing a higher gain change magnitude according to the prior art, when the gain gap is very large and the switching operation is performed, the waveform of the gain curve C would suffer a discontinuous process, i.e. it would generate the gap point P, and thus an audible crackling noise is generated. The gain controlling system 90 of the prior art would easily generate a wobbly waveform.
Therefore, a gain controlling system, a sound playback system, and a gain controlling method thereof are needed to solve the disadvantages of the prior art.